text: In the atmospheric sciences, the vorticity equation can be stated in terms of the absolute vorticity of air with respect to an inertial frame, or of the vorticity with respect to the rotation of the Earth. The absolute version is
  Here,  is the polar () component of the vorticity,  is the atmospheric density, , , and w are the components of wind velocity, and  is the 2-dimensional (i.e. horizontal-component-only) del.